a. Field of the Invention
This invention relates broadly to the laying of a pipeline on a sea bottom. In particular, the invention has regard to method and apparatus for plugging a dry section of the pipeline in response to an influx of water into another section thereof while the pipeline is being laid on sea bottom.
B. Description of the Prior Art
Ordinarily, the laying of a pipeline on a deep sea bottom constitutes connecting a plurality of pipe sections together in end-to-end relationship on a work barge and subsequently lowering the connected sections into the water in a step-by-step manner as the work barge moves towards the direction in which the pipeline is to be laid. In that event, the pipeline forms a catenary between the sea bottom and the work barge which is very susceptible to buckling and breakage. Should breakage occur the previously laid section of the pipeline on sea bottom will of course become flooded with water; this being a major drawback, particularly when the pipeline has to be raised to the water surface for the continuation of the pipelaying operation. That is to say, before the pipeline can be raised to the surface the damaged end of the pipeline must be cut off on sea bottom and the pipeline dewatered with a plugging device to reduce the stresses on the pipeline during the raising thereof. Needless to say, any dewatering operation is time consuming and expensive.